How to insert certificate serial number and ssl verify result to http header both ?

Something like this:

set example {custom_string_foo=[get this data w/out the brackets], custom_string_bar=[get this data too],custom_string_again=[keep getting data until no more instances of custom_string]}

foreach x [split $example ","] {
    log local0. [findstr $x "\[" 1 "\]"]
}

The split command breaks the larger string into list items, and then the foreach loops through that list and extracts the string between the brackets using the findstr command.

The string values don't matter at all. All you care about is that the strings are separated by commas, and that the data you want inside each string is inside square brackets.

set str {test1=[foo],test2=[bar],test3=[blah]}

foreach x [split $str ","] {
    log local0. [findstr $x "\[" 1 "\]"]
}

returns:

foo
bar
blah

You can use two options. The first option is to create a simple list object:

set str {test1=[foo],test2=[bar],test3=[blah]}

set mylist [list]

foreach x [split $str ","] {
    lappend mylist [lindex [split $x "="] 0]
    lappend mylist [findstr $x "\[" 1 "\]"]
}

log local0. "mylist = $mylist"
foreach y $mylist { log local0. $y }

The output of this would be:

mylist = test1 foo test2 bar test3 blah
test1
foo
test2
bar
test3
blah

Where the odd index is the key and the next even index is the value. Or you can use an array:

set str {test1=[foo],test2=[bar],test3=[blah]}

foreach x [split $str ","] {
    set thisarray([lindex [split $x "="] 0]) [findstr $x "\[" 1 "\]"]

}

foreach {index value} [array get thisarray] {
    log local0. "$index = $value"
}

It's output would be:

test1 = foo
test2 = bar
test3 = blah

And then you could access these associative array indices individually.

log local0. $thisarray(test2)